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Course: Science — Third Preparatory

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Science — Third Preparatory

Science — Third Preparatory

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Science — Third Preparatory 2026/2027

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Unit 1 - Force, Motion, Acceleration and Physical Quantities

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Text lesson

Unit 4 — Dating Planet Earth

Science — Third Preparatory

Unit 4 — Dating Planet Earth

1.6 Causes of the diversity of life forms through time

1.6 Causes of the diversity of life forms through time

Scientists give several explanations for the great variety of living things and the appearance of new species through geologic time.

Comparison aspect	Main idea	Example	Keywords
Adaptation to different environments	(the deep sea forests deserts) producing species adapted to each environment	—	deepforestsdesertsproducing
Evolution by natural selection	gradually over long periods or relatively quickly in some cases	—	graduallyoverlongperiods
Accumulated genetic mutations	within a group of organisms	—	withingrouporganisms
Geographical isolation	a group of organisms is separated from the rest of its species by a natural barrier	a mountain range a wide river or a deep valley. Over time this can lead to new species. The steps are: (i) the barrier interrupts gene flow: the two groups no longer mate so genes are no longer exchanged (ii) each group accumulates different mutations independently (iii) natural selection in each different environment preserves the favourable traits in each group (iv) differences grow until mating between the groups becomes impossible and a new species has appeared	grouporganismsseparatedrest

Change and stability. Earth and living things have changed a great deal, but some rock formations stayed relatively stable.
The rock layers record these ancient events.
Check.

Geographical isolation is a cause of the appearance of new species (not of mass extinction).
The fossil record supports (does not deny) the evolutionary link between the Asian elephant and the mammoth.

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